Techcrunch is reporting that GoogleVoice is rolling out out Local Number Portability. That means you can transfer your phone number to Google and they'll be your carrier of record. The story also points out that the next generation of the software for mobile phones (currently Google Voice apps work on iPhones and Androids, and you can manage the service via a mobile version of the web site.)
FWIW...I'm already using the service the way Mike Arrington has described it but I'm not in the reported test group.
Changing SIMS and phones on whims and needs. For example, right now I'm in the middle of a three week, three country business trip that takes me to the UK, France and Spain. All the time I have GoogleVoice pointing to both Skype and Truphone. When I'm online with either my MacBook Air or my Asus Seashell 1008HA I answer calls on Skype just as I could be using Gizmo5 as easily as GoogleVoice and Gizmo peer.
But the real secret to my "staying connected" is how client Truphone overcomes the biggest limitation GoogleVoice has. I can forward my USA based Truphone number to any mobile number once I insert the SIM card. So, as I go from country to country, I simply switch SIMs and Truphone automatically updates to the new mobile number in whichever country I'm in.
The one, two punch combination is easy to use and really cuts down on calling costs. What's more I've even added local numbers in each country which I use as dedicated dial in numbers and can return calls from voice mail messages with simply one touch of a button, meaning my local call is all I'm paying for, while Google Voice does the rest.